1. Field of the Invention
This present disclosure relates to methods of joining ceramics to metal.
2. Related Art
Some medical devices, e.g., visualization devices, include at least one window of an optical material, for example an ultra-hard, chemically inert monocrystalline material such as sapphire. (Natural and synthetic sapphire will be referred to collectively herein as “sapphire”). The window is joined to a metal wall of the device, typically by first brazing or soldering a metallized portion of the window to a metal housing to form a subassembly, and then welding the metal housing of the subassembly to the metal wall of the device. In some cases, the joint between the sapphire window and the metal housing must survive hundreds of autoclave cycles with uncompromised hermeticity.
Windows are typically formed by slicing a sapphire rod into discs, metallizing the discs (or in some cases metallizing the rod, prior to slicing), and polishing the discs to optical quality while taking care not to affect the metal layer. Before or after brazing the metallized portion each window to the metal housing to form the subassembly, the window may be coated with an antireflection coating.